This invention relates generally to a method and system for the detection of liquid cooling status for batteries, as well as for a method and system for correcting coolant flows through batteries in situations where the coolant flow needs to be adjusted.
Lithium-ion and related batteries, collectively known as a rechargeable energy storage system (RESS), are being used in automotive applications as a way to supplement, in the case of hybrid electric vehicles (HEVs), or supplant, in the case of purely electric vehicles (EVs), conventional internal combustion engines (ICEs). The ability to passively store energy from stationary and portable sources, as well as from recaptured kinetic energy provided by the vehicle and its components, makes batteries ideal to serve as part of a propulsion system for cars, trucks, buses, motorcycles and related vehicular platforms. In the present context, a cell is a single electrochemical unit, whereas a battery is made up of one or more cells joined in series, parallel or both, depending on desired output voltage and capacity.
The generation of propulsive power from the RESS also produces significant thermal loads. As such, a RESS-based system preferably includes a cooling system to avoid unacceptably high levels of heat being imparted to the batteries and ancillary equipment. Keeping excess heat away from these, as well as other, thermally-sensitive components helps to promote their proper operation and long life. In one particular form, such a cooling system may include the passive or active circulation of a liquid coolant in, around or otherwise thermally adjacent to the batteries or other heat-generating components. One or more heat exchangers may be used to convey excess heat away. For example, the Chevrolet Volt, a vehicle manufactured by the Assignee of the present invention, has three heat exchangers for use in conjunction with its RESS, including a liquid-to-air radiator, a high voltage electric heater and a refrigerant-to-coolant chiller. Controllers monitor for loss of isolation between the high voltage system and the rest of the vehicle, as well as for electrical shorts within the battery.
Designers frequently take the possibility of accidents into consideration when designing a vehicular platform. With the advent of battery power (and the concomitant large amounts of electrical energy produced thereby), it is preferable to likewise design the vehicle to be resistant to accidents or related impact to avoid the uncontrolled release of significant levels of electrical current. One particular concern for battery designers pertains to the coolant discussed above, where leakage into the battery may provide an efficient and unintended path for the conveyance of electrical energy in the event of a disruptive event, such as due to component wear or the aforementioned accident. In one undesirable form, the coolant may deliver the current to internal electronic components—such as circuit board or the like—that are not configured to accept large amount of current. Exacerbating this concern is that there may be a latency period between the time the damage is incurred and when a leakage may progress to sensitive electrical components. In one form, it may take days to weeks following a damage-inducing event (such as a crash) for the coolant to leak into the battery or batteries and the sensitive electronics contained therein.
The use of a multi-pronged heat management equipment (such as that mentioned above in conjunction with the Chevrolet Volt) is useful for its intended purpose. Nevertheless, it would be beneficial to also provide early detection of loss if coolant into the battery following an accident or related incident where a rapid release of electrical or thermal energy could occur. It would be further beneficial to implement automated corrective actions in the event of a pending discharge of energy when coolant has leaked into the battery.